1. Field of the Invention
The present invention relates to a backlight unit, and more particularly, to a backlight unit capable of using a reduced number of light sources, thereby reducing the manufacturing costs.
2. Discussion of the Related Art
Display devices are classified into an emissive display device such as a cathode ray tube, an organic electro-luminescence display device, or a plasma display device (PDP), which can emit light by itself, and a non-emissive display device such as a liquid crystal display (LCD) device, which cannot generate light by itself, so that it requires a separate light source.
A general LCD device includes two display panels provided with electric field generating electrodes, and a liquid crystal layer interposed between the display panels. The liquid crystal layer has dielectric anisotropy. In the LCD device, an electric field is generated at the liquid crystal layer as a voltage is applied to the electric field generating electrodes. The intensity of the electric field is adjusted as the voltage is varied. In accordance with the adjustment of the electric field intensity, the transmittance of light passing through the liquid crystal layer is controlled. Thus, a desired image is obtained. The light may be light generated from a separate artificial light source provided at the LCD device, or may be natural light.
For the light source of the LCD device, several lamps are typically used. In particular, for a light source capable of uniformly supplying light to the overall portion of the liquid crystal panel at the back surface of the liquid crystal panel, a fluorescent lamp such as an external electrode fluorescent lamp (EEFL) or a cold cathode fluorescent lamp (CCFL), or a light emitting diode (LED) is used.
The most excellent advantage of an LED backlight unit for an LCD device, for which active research and development are currently conducted, is in that it is possible to provide optimal color sensation desired by the user.
However, the LED, which is used for the light source of the backlight unit exhibits an abrupt variation in light efficiency caused by heat. For example, the LED sensitively responds to the external environment or internal heat source of the LCD device, so that the color balance of the LED may collapse.
In particular, the above-mentioned problem is severe in a backlight unit used for a large-size LCD device because the backlight unit uses a large number of LEDs. Furthermore, there is a problem of an increase in the manufacturing costs due to the increased number of LEDs.